Characteristics of Photoreceptor PDE (PDE6): similarities and differences to PDE5

Abstract

Phosphodiesterase 6 (PDE6) is highly concentrated in the retina. It is most abundant in the internal membranes of retinal photoreceptors, where it reduces cytoplasmic levels of cyclic guanosine monophosphate ( cGMP) in rod and cone outer segments in response to light. The rod PDE6 holoenzyme comprises alpha and beta catalytic subunits and two identical inhibitory gamma subunits. Each catalytic subunit contains three distinct globular domains corresponding to the catalytic domain and two GAF domains ( responsible for allosteric cGMP binding). The PDE6 catalytic subunits resemble PDE5 in amino-acid sequence as well as in three-dimensional structure of the catalytic dimer; preference for cGMP over cyclic adenosine monophosphate ( cAMP) as a substrate; and the ability to bind cGMP at the regulatory GAF domains. Most PDE5 inhibitors inhibit PDE6 with similar potency, and electroretinogram studies show modest effects of PDE5 inhibitors on visual function - an observation potentially important in designing PDE5-specific therapeutic agents.

Publication Date

1-1-2004

Journal Title

International Journal of Impotence Research

Publisher

Nature Publishing Group

Digital Object Identifier (DOI)

10.1038/sj.ijir.3901212

Scientific Contribution Number

2162

Document Type

Article

Rights

© 2004 Nature Publishing Group All rights reserved

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